Discipline: Ecology Environmental and Earth Sciences
Subcategory: Environmental Engineering
James Fluke - University of New Mexico
Co-Author(s): Ricardo Gonzalez-Pinzon, University of New Mexico, Albuquerque, New Mexico
Bacterial surface water impairment due to fecal contamination accounts for 4 billion episodes of illness and 2.2 million deaths yearly worldwide according to the World Health Organization. It is also the largest single cause of impaired stream miles in the US (30%) according to the EPA. Human exposure to fecal contamination is considered a health risk and is tracked using fecal indicator bacteria (FIB) groups such as E. coli and fecal coliforms which indicate the likely presence of pathogens. Lack of data on response to environmental conditions and conventional testing limitations (18-24 h sample incubation) means we cannot predict in-stream FIB behavior. Particularly in arid regions, bacterial impairment will demand increasing attention as wastewater effluents from growing populations become less dilute due to decreasing groundwater recharge and streamflows and water demands rise.
The objective of this work is to investigate the seasonal dynamics of FIB in the arid Rio Grande river near Albuquerque (~1 million inhabitants), which is classified by the EPA as impaired by E. coli bacteria. In this reach, concentrations exceed water quality standards year-long, with dramatic episodes exceeding standards (>3 orders of magnitude) in summer months1, when temperatures are highest and short precipitation events coincide with low river flows. Microcosm experiments and fixed-point monitoring of E. coli levels in river water and sediment have shown: 1) FIB levels positively correlate with water temperature, 2) FIB in streambed sediments are present in concentrations typically higher than in overlying surface water, 3) net regrowth (observed over periods of 1-5 days) of FIB in extracted surface water and sediment/water microcosms frequently precedes net decay. Water and sediment samples were analyzed using EPA approved Membrane Filtration and Multiple Tube Fermentation respectively (methods comparable on log-scale3). Blanks were run at a frequency of 10% and duplicate tests show results are comparable within an order of magnitude. This confirms the hypothesis that significant sources of FIB live in contact with the waterway and shows that FIB dynamics are not negligible for water quality regulation. A better understanding of the driving factors affecting FIB dynamics is needed and this is a step in developing cohesive data sets and identifying challenges for calibration and validation of descriptive and predictive models.
1US EPA, June 2010. ‘US EPA-Approved Total Maximum Daily Load for the Middle Rio Grande Watershed,’ https://www.env.nm.gov/swqb/Rio_Grande/Middle/index.html
2Y. A. Pachepsky and D. R. Shelton, ‘Escherichia Coli and Fecal Coliforms in Freshwater and Estuarine Sediments,’ Critical Reviews in Environmental Science and Technology 41, no. 12 (April 28, 2011): 1067?1110.
3Qualls RG, Chang JC, Ossoff SF, and Johnson JD. 1984.’Comparison of Methods of Enumerating Coliforms After UV Disinfection.’ Applied and Environmental Microbiology 48 (4): 699-701.Fluke_ECNConference2018_AbstractFinal.docx
Funder Acknowledgement(s): Funding has been provided for sample analysis by the New Mexico Water Resources Research Institute (NMWRRI) Student Research Grant Program (surface water samples) and the New Mexico Environment Department (NMED) through the Ciudad Soil and Water Conservation District (CSWCD) (sediment samples). Laboratory space and equipment has been provided through a NSF Centers of Research and Excellence in Science and Technology (CREST) grant to the University of New Mexico Center for Water and the Environment.
Faculty Advisor: Ricardo Gonzalez-Pinzon, firstname.lastname@example.org
Role: Development of project idea, procurement of funding, data generation, and data interpretation with guidance and input from academic advisor.